Telescopic switch for isolated phase bus

ABSTRACT

A telescopic switch for an isolated phase bus system is disclosed. The switch includes a hollow cylindrical blade which resides within one section of hollow bus and telescopes between first and second positions to engage and disengage, respectively, the jaw contacts on a second section of the bus. The mechanism for moving the blade includes a gear reduction assembly located substantially internally of the bus which houses the hollow blade. The gear reduction assembly includes a driven gear connected to an external driving shaft through an insulator, and a driving gear linked to the blade in a dead center crank arrangement to achieve high mechanical advantage at the end of the closing stroke. A single external drive shaft is connected in tandem through insulators to the gearing assembly of each of the phases whereby the telescopic switches of all phases may be operated simultaneously.

PATENIEUFEB man' 'i :1562465 snm 1 nr 7 IZELZ United States Patent lll] 3,562,465

[72] Inventor Joseph A. Turgeon FOREIGN PATENTS T0l0m0r OMBI'O. Canada 648,925 7/ 1937 Germany 200/1 48(2) 121 1 Appl N0 7694178 860,245 2/1961 Great Britain.. 20o/148].2) 1221 Filed Oct. 2l, 1968 919,024 2/1963 Great Britain.. 20o/163 1451 Patented Feb-9,197] 583,668 10/1958 naly 2o0/153(.16) [73] Assignee l-T-E Circuit Breaker (Canada) Limited port Credit Ontario, Canada Pnr'nary Examiner-H. O. Jones a limited liabimy company of Canada Assistant Examiner-Robert A. Vanderhye Attorney-Ostrolenk, Faber, Gerb & Soffen [54] TELESCOPIC SWITCH FOR ISOLATED PHASE BUS 1l Claims, 13 Drawing Figs.

ABSTRACT: A telescopic switch for an isolated phase bus system is disclosed. The switch includes a hollow cylindrical blade which resides within one section of hollow bus and telescopes between first and second positions to engage and disengage, respectively, the jaw contacts on a second section of the bus. The mechanism for moving the blade includes a gear reduction assembly located substantially internally of the bus which houses the hollow blade. The gear reduction assembly includes a driven gear connected to an external driving shaft through an insulator, and a driving gear linked to the blade in a dead center crank arrangement to achieve high mechanical advantage at the end of the closing stroke. A single external drive shaft is connected in tandem through insulators to the gearing assembly of each of the phases whereby the telescopic switches of all phases may be operated simultaneously.

PATENTEU fea 91971 lllllllllllllllllllll -hmhwhrll 1 TELESCOPIC SWITCH FOR ISOLATEI) PHASE BUS BACKGROUND OF THE INVENTION The present invention relates to disconnect switches used in isolated phase busbar systems, and more particularly to such disconnect switches of the telescopic type. j

Isolated phase bus systems are large and require a great deal of space. Since this space is at a premium it is desirable to insure efficient design and planning of such systems. For this reason it has been found highly advantageous to use telescopic disconnect switches wherein the blade moves along its own axis to effect connection and disconnection. The advantages of such telescopic disconnect switches for use in isolated phase bus systems can be seen in U. S. Pat. Nos. 2,517,435 issued Aug. l, 1950; 2,679,567 issued May 25, l954; 2,889,435 issued Jun. 2, i959; and 2,889,436 issued Jun. 2, 1959.

While the previous telescopic switches for isolated phase bus systems have substantially decreased the amount of space necessary for the operation of disconnect switches in such systems, they have at the same time created additional problems. Thus typical operating mechanisms for such switches have been in the form of a power screw or rack and pinion arrangements, the mechanical advantages of which remain uniform throughout a contact opening or closing operation. However, and especially in high current systems which require large current carrying contact structures, more force is required to open and close the cooperating contacts than during the intermediate movement of the movable contact blade. Thus with the prior art, constant force devices, relatively large and cumbersome mechanical arrangements are necessary to generate large forces required only for a small portion of the opening and closing strokes, while such mechanisms are oversized and unnecessary during the intermediate contact motion. l

Furthermore, operation of the prior art telescopic blade switches presents problems, particularly in multiphase systems, because of the large external force necessary to move the blades. Specifically, in multiphase systems where the telescopic switches of all phases are operated by a single external shaft having insulators along the shaft between each of the phases, the external force necessary to operate the switches puts great torsional stresses on the insulators making them susceptible to breakage.

The present invention eliminates the above problems of the previous telescopic switches for isolated phase bus systems by the provision of a new and novel telescopic switch and operating mechanism therefor. In a preferred embodiment of the instant invention there is provided a hollow telescopic blade movable into and out of one section of a bus by means of a gear assembly secured to the bus conductor within the bus run housing and substantially within the conductor. An output i linkage of the gear assembly is connected to the movable blade in a dead center crank arrangement, to be explained in greater detail, whereby greater mechanical force is developed during the separation or engagement of the contact blade and its cooperating stationary contact jaw. In this manner, the overall mechanical system is smaller since it can be tailored to produce only the smaller force required during intennediate blade motion.

Furthennore, to reduce torsion on the insulators of the switch, the instant invention locates the gear reduction assemblies of each phase of a multiphase system between portions of the single drive shaft of the system and each of the movable contact blades.

It is therefore one object of the instant invention to provide a new and novel telescopic disconnect switch for isolated phase bus runs.

It is a further object of the instant invention to provide a new and novel telescopic switch which may be preassembled at the factory and may be easily and conveniently installed within an isolated phase bus system.

A further object of the instant invention is to provide an operating mechanism for a telescopic disconnect switch consisting of a gear reduction mounted substantially within a bus conductor.

lt is a further object of the instant invention to provide the gear assembly for a telescopic switch which includes as an output drive, a dead center crank arrangement whereby larger mechanical forces may be generated during the opening and closing of the switch.

Another object of the instant invention is to provide a tele` scopic disconnect switch for a multiphase isolated phase bus system whereby the telescopic switches of each phase are simultaneously operated by an external drive shaft requiring relatively little force to move the telescopic blades of all of thc switches and keeping the torsional stresses on thc drive shaft relatively low.

The above objects, features and advantages. along with other objects, features and advantages will become apparent upon a reading of the following description of a preferred em bodiment of the instant invention in conjunction with the drawings, as follows:

FIG. l is a perspective view of a telescopic switch of the instant invention as it would be situated within a three-phase isolated phase busbar system;

FIG. 2 is a cross-sectional end view of the switch of FIG. l taken along the drive shaft of the telescopic disconnect switch with the telescopic blade and gearing assembly removed;

FIG. 2a is a plan view of the disc seal on the drive shaft of FIG. 2;

FIG. 2b is a plan view of the flange on the drive shaft of FIG. 2;

FIG. 3 is a side view of one phase of the switch of FIG. I with the housing partially removed;

FIG. 3a is a side view of one phase of the switch of FIG. I but with the telescopic switch blade in closed position;

FIG. 4 is an enlarged view of a portion of FIG. 3 but drawn in section to show the gearing mechanism for the blade;

FIG. 5 is a bottom cross-sectional view of the conductor and blade of FIG. 4;

FIG. 6 is an end view of thc conductor and blade of FIG. 4 taken from the right end;

FIG. 7 is a side view of the jaw contact assembly of the telescopic switch of FIG. 3 drawn partially in sections;

FIG. 8 is an endview of the jaw contact assembly of FIG. 7 taken from the left end; v

FIG. 9 shows a perspective view of the gearing mechanism and housing therefor as secured to a section of the bus conductor of the switch of the instant invention with parts of the housing broken away; and

FIG. l0 shows a perspective view of the housing for the gearing mechanism of the telescopic switch of the instant invention.

Referring first to FIG. l, there is shown the three-phase telescopic switch l0 of the instant invention comprising the centrally located bus'conductors l1, l2 and I3 which are isolated from one another by metallic housings I4, I5 and I6, respectively. Although not illustrated in FIG. l, it is to be understood that a switch l0 constructed in accordance with the instant invention is adapted to be inserted in a three-phase isolated phase busbar distribution system at a point where it is desired to have circuit opening and closing capabilities. It is a particularly advantageous feature of the instant invention that the switch l0 may be completely assembled at the factory and easily inserted within the distribution system (not shown), for example, by means of appropriate end fittings such as 17 which would join the housings 14, 15 and I6 to the corresponding housings of the distribution system. Similarly, appropriate connectors (not shown) would be utilized to join the busbars ll, I2 and I3 of the switch l0 to the corresponding conductor of the distribution system. It should be understood that although a three-phase system is shown the novel telescopic switch may be used for any type of system employing a housed or enclosed bus.

Each of the bus housings 14,15 and 16 are metallic cylinders supported by interfaced connecting brackets I8 and 19 and hanger members 20 and 2l. One manner of supporting the housings of such isolated phase bus systems is described in U. S. Pat. No. 3,243,502 issued Mar. 29, l966 to the applicant and assigned to the assignee of the instant application. The bus conductors are supported within the housing by insulator members 22, 23, 24 and 25, as enumerated for example with respect to bus conductor l1.

Each of the housings for the conductors also include a glass window providing visibility of the telescoping blades and jaw Contact structure associated with each bus conductor. For instance, housing 14 is provided with window 26 sealed in an aluminum plate 27 having a contour corresponding to the contour of the housing 14. Rubber seals 28 and 29 may be employed to prevent the entrance of contaminants. As shown in FIG. l, each of the housings is also provided with a cover as for instance 30 on housing 14. The cover 30 may have a contour extending away from the housing to make room for the gearing mechanism of the telescopic switch within the housing as to be explained in greater detail hereinafter. The protrusion of the cover 30 from the housing I4 is to permit electrical clearance to the gearing mechanism.

Connected externally of the housings 14, l and 16, is a drive mechanism including a firstshaft 31 having a wheel 32 secured at one end thereof for rotation of the shaft 31 by hand. A gear box 33 is connected at the second end of shaft 31 and may include two beveled gears whereby the shaft 3l is interlocked with the shaft 34 to cause rotation of shaft 34 upon the rotation of shaft 3l.

Referring next to FIG. 2, there is shown a cross-sectional end view of the switch of FIG. 1 taken along the shaft 34 from the rear end of the bus run. The view of FIG. 2 primarily shows the drive shaft 34 for controlling the telescopic switch of the instant invention and eliminates the .details of the remaining aspects of the bus run and telescopic switch. The drive shaft 34 is connected to insulator 35 which may be made of porcelain or other suitable material. The drive shaft 34 is connected to the insulator 35 by means of a disc-shaped flange 36 securely attached to the shaft 34 and bolts 37 which secure the flange 36 to flange 38 of the insulator 35. Insulator 35 is connected at its opposite end by means of a similar flange ar rangement to a second portion of the drive shaft 34a which is to be connected to the gearing assembly for controlling the telescopic switch of the instant invention. The insulator 3S serves as insulation between the telescopic switch and the drive sha 34 which, for safety reasons, is also grounded.

The drive shaft 34a has been shown broken away in the section where it is to be connected to the gearing mechanism. The opposite ends of drive shaft 34a is connected to insulator 39 which is connected to a third portion of the drive shaft 34h. The connections are all similar to the flange arrangements previously described. The drive shaft 34h has a flange 40 at its opposite end for connection to the flange 4l of the drive shaft 34e` associated with a second phase of the isolated phase bus system. Each of the additional phases has insulators along the drive shaft as previously described for the purpose of maintaining the isolation of each of the phases from the others.

Insulation means is also provided to keep the drive shaft 34 insulated from the housings 14, and 16 of the bus run. To that effect holes are provided at 41a in the housing 14, l5 and 16 permitting the flanges of the shaft 34 to pass therethrough. In order to adequately seal the shaft 34, an insulated support consisting of a hard rubber disc 42 and a flange 43 bolted to the housing 14 by means of bolts 44 is provided. Disc 42 and flari'ge 43 can be seen more clearly in FIGS. 2a and 2b.

Rubber spacers for the shafts 34h and 34e` are shown between the housings 14 and 15, at 4lb. These rubber spacers provide for some misalignment. In addition, a cover 45 is provided for safety, as it is easier to ground than a rotating shaft. Similarly, insulators are provided between housings l5 and 16.

Referring next to FIG. 3, there is shown a side view of one phase of the switch l0 with the housing partially removed. The conductor has been numbered Il corresponding to the first conductor of the switch of FIG. 1. The conductor 1l is separated into two sections with the right portion IIa including the jaw contact assembly generally designated as 50 and the left section including the blade assembly generally designated as 60. The conductor Il is supported in the housing I4 by means of insulators as previously described with respect to FIG. l.

The jaw contact section of the telescopic switch includes a plurality of fingers 5l held on a disc 52 by means of garter springs 53, as can bc seen most clearly in FIG. 7. The disc 52 is round and is secured to theconductor Il by means of a stud 54 and a nut 55 which are fastened to a cylindrical member 56 attached to conductor 11a. Conductor Ila is supported by insulators 58, 59, 58a and 59a within the housing 14.

The blade assembly 60 generally shown in FIG. 3 and shown in detail in the enlarged view of FIG. 4 includes a blade 61 movable into and out of the lefthand section of conductor l l.v The blade is hollow and has a round cross section as seen in FIG. 6. An interface 62 is provided having a rectangularly shaped outer perimeter corresponding to thc interior cross section of the conductor ll and having an inner bore of round cylindrical shape with a diameter equal to the largest diameter of the telescopic blade 61. The interface 62 enables the use of a round telescopic blade even though the conductor ll has an interior hollow cross section of rectangular shape.

The interface 62 is provided with a rim 63 which extends around the perimeter of its extreme right-hand edge. This rim is provided for cooperation with the contact fingers 64 which are held upon the interface by garter springs 65. As can be seen, the garter springs 65 cooperate to secure the Contact fingers 64 around the periphery of the interface 62. The garter spring 65 also exerts an inward radial force upon the contact fingers 64 to ensure proper electrical contact between the contact fingers 64 and the telescopic blade 6I. Thus` the electrical circuit between the conductor ll and the telescopic blade 6l is maintained.

The telescopic blade 61 has been designed to maximize the electrical engagement between the blade and the contact fin gers and at the same time minimize the force necessary to move the blade 6l between its engaged and disengaged positions. In particular, the blade 6I has been provided in cylindrical form with the outer diameter of the central portion of the blade 66 being smaller than the outer diameters of its two end portions 67 and 68, respectively. In this manner, when the blade 6l is in engagement with the jaw contacts 5l, as shown in FIG. 3a, the portion 68 of the blade is tightly wedged in engagement with the jaw contacts 541 and the portion of the blades 67 is tightly wedged in engagement with the contacts 64. On the other hand, when the blade is to be moved out of engagement with the jaw contact 5l, the portion 66 of the blade 6l passes through the hole formed by the contact 64. Since the portion 66 is of a smaller diameter than the end portion of the blade 6l, the frictional engagement of the portion 66 with the contact fingers 64 will be substantially decreased thereby permitting the movement of the blade with less force than would otherwise be required. Furthermore, this eliminates the frictional wear and tear caused to the contact fingers 64 and the blade 61.

Considering next the gearing assembly of the telescopic switch of the instant invention, reference is made primarily to FIGS. 4. 5 and 9. The shaft 34a connected between insulators 35 and 39 includes a portion 70 having teeth therein. The por tion 70 of shaft 34a engages a gear 7l. Gear 7l has a shaft portion 72 extending therefrom and also having teeth thereon. The portion 72 is of a considerably smaller diameter than gear 7l. The teeth of extension 72 engage the gear 73. Attached to gear 73 are the links 74 and 75. The links 74 and 75 are secured to the blade 6l by means of a pin 76 having a central sleeve 77 and washers 78 and 79 for positioning links 74 and 75.

As can be seen, rotation of the wheel 32 of FIG. l causes rotation of shaft 3l and rotation of drive shaft 34. This causes the rotation of the insulator 35 and shaft 34a and thereby gear portion 70 of the shaft 34a. Upon rotation of gear portion 70,

the gear 7l is caused to rotate and thereby' extension 72 rotates to move the gear 73, Movement of gear 73 causes the displacement of links 74 and 75 and, hence. the movement of blade 6I. Since the gear portion 70 of shaft 34a has a substantially smaller diameter than gear 7l, and since gear 72 has a substantially smaller diameter than gear 7l and gear 73, the force necessary to rotate the shaft 34 is substantially less than the thc force necessary to move the blade 6l without this gear reduction relationship. Furthermore. since the gear reduction occurs between the shaft 34a and the blade 61 rather than between the wheel 32 and the shaft 34, the insulators 35 and 39 benefit from the gear reduction relationship and do not experience the great torsional stresses which they would otherwise be subjected to.

Furthermore, and as best illustrated in FIG. 4, the linkage 74, 75 is secured to gear 73 in such a manner as to achieve dead center crank operation just when the blade 61 is urged into engagement with the contacbstructure 50 (and the enlarged portion 67 of the blade 6l engages the interface 62). Thus, the line 74a is the line of actibn of the link 74 at the end of the closing stroke, and for that matter at the initiation of the opening operation. This dead center position is the position for maximum compression and tension forces. As seen in FIG. 4,

Torque at Point B Force (F) Distance Y and as the angle aapproaches 180, Y(a sin a) approaches 0, therefore,

Torque at Point B Force Y--rO that is, a distance Y approaches zero 0, the force (F) will theoretically approach infinity. Thus, a relatively small mechanism is possible but the larger forces required at the end of the stroke is still possible.

As seen in FIGS. 9 and l0, the gearing assembly is provided with the housing generally shown as 80. The housing 80 enables the assembling of the gear assembly as a preassembly which can be installed as a unit in the housing. The housing includes flanges 8l and 82 through which the shaft 34a passes and between which the gear portion 70 is ultimately situated. Flanges 83 and 84 include bores for the mounting of gears 7l and 72 in cooperative relationship with the gear 70 of shaft 34a. Finally, flange 85 and a second flange opposite thereto, not shown, include bores therethrough for the mounting of gear 73 in cooperative relationship with the extension 72 of gear 7l. Bolts 86 secure the two portions 87 and 88 of the housing together to maintain the gearing assembly as a single unit. Flange 89 is provided around the housing 80 and includes holes 90 extending therethrough permitting the fastening of the housing 80 to the conductor l1 by means of bolts.

It should be appreciated from the above description of the instant invention that a new and novel telescopic switch for isolated phase bus runs has been provided with a new and novel operating mechanism consisting of a gear reduction assembly situated within the bus conductors and drivable with minimum force through drive shaft and insulators connected between the drive shafts and the gearing assembly. In this manner, the insulators are not subjected to great torsional stresses and the drive shaft may be easily rotated by hand to control the operating mechanism and telescopic switch. Furthermore, the telescopic blade of the new and novel telescopic switch is shaped in a manner to enhance the movability of the telescopic switch while at the same time enhancing the electrical contact between the telescopic blade and the bus conductor and jaw contacts.

While the instant invention is described with respect to one first and second hollow conductors in axial alignment having a gap therebetween;

first movable conductor means located within said first hollow conductor and movable between a first position in which said movable conductor means is electrically isolated from said second hollow conductor and a second position in which said movable conductor means is electrically connected to said second hollow conductor;

first gear reduction means located substantially within said first conductor and linked to said movable conductor means for moving said movable conductor means between its first and second positions;

wherein said second hollow conductor includes contact jaw means which frictionally receives said first movable conductor means when said first movable conductor means moves to its second position; and

wherein said first gear reduction means is linked to said first movable conductor means in a dead center crank operating relationship which generates higher force on said first movable conductor means as it reaches its second position and frictionally engages said contact jaw means,

2. The electrical apparatus of claim l, wherein said first gear reduction means includes a rotatable output crank and a driving link secured at one end to a peripheral point on said crank and at its other end to said first movable conductor means, said peripheral point being selected relative to the pivotal axis of said output crank such that when said first movable conductor means approaches its second position in frictional engagement with said contact jaw means, said peripheral point will approach an imaginary straight line joining said pivotal axis and the point of connection between said other end of said link and said first movable conductor means.

3. The electrical apparatus of claim 1, wherein said first movable conductor means has enlarged cross-sectional areas at opposite ends thereof relative to a reduced cross-sectional area intermediate said opposite ends, and said contact jaw means frictionally engages one of said enlarged ends when said first movable conductor means is in its second position.

4. The electrical apparatus of claim 3, and further including bearing means supporting said first movable conductor means within said first hollow conductor, said bearing means having an outside diameter corresponding to the inside diameter of said first hollow conductor, and an inside diameter slightly larger than said reduced cross-sectional area of said first movable conductor means, whereby said first movable conductor means will require less force to move between said first and second positions to finally engage said contact jaw means at its second position.

5. The electrical apparatus of claim 4, wherein said bearing means includes spring biased contact means for firmly engaging the other of said enlarged ends of said first movable contact means when said first movable contact means is in its second position.

6. The electrical apparatus of claim 4, wherein said first gear reduction means is linked to said first movable conductor means in a dead center crank operating relationship which generates higher force on said first movable conductor means as it reaches its second position and frictionally engages said contact jaw means.

7. The electrical apparatus of claim 6, wherein said first gear reduction means includes a rotatable output crank and a driving link secured at one end to a peripheral point on said crank and at its other end to said first movable conductor means, said peripheral point being selected relative to the pivotal axis of said output crank such that when said first movable conductor means approaches its second position in frictional engagement with said contact jaw means, said peripheral point will approach an imaginary straight line joining said pivotal axis and the point of connection between said other end of said link and said first movable conductor means.

8. The electrical apparatus of claim l, and further including:

third and fourth hollow conductors in axial alignment having a gap therebetween;

second movable conductf'r` means located within said third hollow conductor and movable between a first position in which said second movable conductor means is electrically isolated from said fourth hollow conductor and a second position in which said movable conductor means is electrically connected to said fourth conductor;

second gear reduction means located substantially within said third conductor and linked to said second movable conductor means for moving said movable conductor means between its first and second positions;

wherein said fourth hollow conductor includes second contact jaw means which frictionally receives said second movable conductor means when said second movable conductor means moves to its second position;

wherein said second gear reduction means is linked to said second movable conductor means in a dead center crank operating relationship which generates higher force on 8 said second movable conductor means as it reaches its second position and frictionally engages said second contact jaw means; and

common drive means for operating said tirst and second gear reduction means.

9. The electrical apparatus of claim 8, wherein said common drive means includes a shaft arrangement including at least one insulator between said first and second gear reduction means to provide electrical insulation therebetween.

l0. The electrical apparatus of claim 9, wherein said first and second and third and fourth conductors are insulatingly supported within first and second metallic housings, respectively.

ll. The electrical apparatus of claim 9, wherein said common drive means is electrically isolated from said first and second metallic housings. 

1. Electrical switching apparatus comprising: first and second hollow conductors in axial alignment having a gap therebetween; first movable conductor means located within said first hollow conductor and movable between a first position in which said movable conductor means is electrically isolated from said second hollow conductor and a second position in which said movable conductor means is electrically connected to said second hollow conductor; first gear reduction means located substantially within said first conductor and linked to said movable conductor means for moving said movable conductor means between its first and second positions; wherein said second hollow conductor includes contact jaw means which frictionally receives said first movable conductor means when said first movable conductor means moves to its second position; and wherein said first gear reduction means is linked to said first movable conductor means in a dead center crank operating relationship which generates higher force on said first movable conductor means as it reaches its second position and frictionally engages said contact jaw means.
 2. The electrical apparatus of claim 1, wherein said first gear reduction means includes a rotatable output crank and a driving link secured at one end to a peripheral point on said crank and at its other end to said first movable conductor means, said peripheral point being selected relative to the pivotal axis of said output crank such that when said first movable conductor means approaches its second position in frictional engagement with sAid contact jaw means, said peripheral point will approach an imaginary straight line joining said pivotal axis and the point of connection between said other end of said link and said first movable conductor means.
 3. The electrical apparatus of claim 1, wherein said first movable conductor means has enlarged cross-sectional areas at opposite ends thereof relative to a reduced cross-sectional area intermediate said opposite ends, and said contact jaw means frictionally engages one of said enlarged ends when said first movable conductor means is in its second position.
 4. The electrical apparatus of claim 3, and further including bearing means supporting said first movable conductor means within said first hollow conductor, said bearing means having an outside diameter corresponding to the inside diameter of said first hollow conductor, and an inside diameter slightly larger than said reduced cross-sectional area of said first movable conductor means, whereby said first movable conductor means will require less force to move between said first and second positions to finally engage said contact jaw means at its second position.
 5. The electrical apparatus of claim 4, wherein said bearing means includes spring biased contact means for firmly engaging the other of said enlarged ends of said first movable contact means when said first movable contact means is in its second position.
 6. The electrical apparatus of claim 4, wherein said first gear reduction means is linked to said first movable conductor means in a dead center crank operating relationship which generates higher force on said first movable conductor means as it reaches its second position and frictionally engages said contact jaw means.
 7. The electrical apparatus of claim 6, wherein said first gear reduction means includes a rotatable output crank and a driving link secured at one end to a peripheral point on said crank and at its other end to said first movable conductor means, said peripheral point being selected relative to the pivotal axis of said output crank such that when said first movable conductor means approaches its second position in frictional engagement with said contact jaw means, said peripheral point will approach an imaginary straight line joining said pivotal axis and the point of connection between said other end of said link and said first movable conductor means.
 8. The electrical apparatus of claim 1, and further including: third and fourth hollow conductors in axial alignment having a gap therebetween; second movable conductor means located within said third hollow conductor and movable between a first position in which said second movable conductor means is electrically isolated from said fourth hollow conductor and a second position in which said movable conductor means is electrically connected to said fourth conductor; second gear reduction means located substantially within said third conductor and linked to said second movable conductor means for moving said movable conductor means between its first and second positions; wherein said fourth hollow conductor includes second contact jaw means which frictionally receives said second movable conductor means when said second movable conductor means moves to its second position; wherein said second gear reduction means is linked to said second movable conductor means in a dead center crank operating relationship which generates higher force on said second movable conductor means as it reaches its second position and frictionally engages said second contact jaw means; and common drive means for operating said first and second gear reduction means.
 9. The electrical apparatus of claim 8, wherein said common drive means includes a shaft arrangement including at least one insulator between said first and second gear reduction means to provide electrical insulation therebetween.
 10. The electrical apparatus of claim 9, wherein said first and second and third and fourth conductors are insulaTingly supported within first and second metallic housings, respectively.
 11. The electrical apparatus of claim 9, wherein said common drive means is electrically isolated from said first and second metallic housings. 